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pknlusr: fix hard-coded netlink multicast group ID

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The group ID used by xt_pknock is configurable, but pknlusr hard-codes
it. Modify pknlusr to accept an optional ID from the command line.
Group IDs range from 1 to 32 and each ID appears in the group bitmask
at position `group_id - 1`.

Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
This commit is contained in:
Jeremy Sowden
2020-10-25 14:15:55 +01:00
committed by Jan Engelhardt
parent 05cacbe84c
commit 63fb5d3490
1 changed files with 35 additions and 4 deletions
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39
extensions/pknock/pknlusr.c
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@@ -7,15 +7,21 @@
#include <arpa/inet.h> #include <arpa/inet.h>
#include <linux/netlink.h> #include <linux/netlink.h>
#include <linux/connector.h> #include <linux/connector.h>
#include <errno.h>
#include <libgen.h>
#include <limits.h>
#include "xt_pknock.h" #include "xt_pknock.h"
#define GROUP 1 #define DEFAULT_GROUP_ID 1
#define MIN_GROUP_ID DEFAULT_GROUP_ID
#define MAX_GROUP_ID \
(sizeof((struct sockaddr_nl){0}.nl_groups) * CHAR_BIT)
int main(void) int main(int argc, char **argv)
{ {
int status; int status;
int group = GROUP; unsigned int group_id = DEFAULT_GROUP_ID;
struct sockaddr_nl local_addr = {.nl_family = AF_NETLINK}; struct sockaddr_nl local_addr = {.nl_family = AF_NETLINK};
int sock_fd; int sock_fd;
size_t nlmsg_size; size_t nlmsg_size;
@@ -23,6 +29,31 @@ int main(void)
struct cn_msg *cn_msg; struct cn_msg *cn_msg;
struct xt_pknock_nl_msg *pknock_msg; struct xt_pknock_nl_msg *pknock_msg;
if (argc > 2) {
char *prog;
if (!(prog = strdup(argv[0]))) {
perror("strdup()");
} else {
fprintf(stderr, "%s [ group-id ]\n", basename(prog));
free(prog);
}
exit(EXIT_FAILURE);
}
if (argc == 2) {
long n;
char *end;
errno = 0;
n = strtol(argv[1], &end, 10);
if (*end || (errno && (n == LONG_MIN || n == LONG_MAX)) ||
n < MIN_GROUP_ID || n > MAX_GROUP_ID) {
fputs("Group ID invalid.\n", stderr);
exit(EXIT_FAILURE);
}
group_id = n;
}
sock_fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR); sock_fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR);
if (sock_fd == -1) { if (sock_fd == -1) {
@@ -30,7 +61,7 @@ int main(void)
exit(EXIT_FAILURE); exit(EXIT_FAILURE);
} }
local_addr.nl_groups = group; local_addr.nl_groups = 1U << (group_id - 1);
status = bind(sock_fd, (struct sockaddr *)&local_addr, sizeof(local_addr)); status = bind(sock_fd, (struct sockaddr *)&local_addr, sizeof(local_addr));
if (status == -1) { if (status == -1) {
perror("bind()"); perror("bind()");